The spirit Safe - Blog post from Whisky Magazine

How a spirit safe works
After the distillation process in the boiler (spirit still), the fresh distillate flows into the spirit safe. As it flows through, the liquid splits into three components:

Foreshot (often called the head)
Middle cut (the heart = new make)
Feints (also called the tail)

Of these three components, only the middle cut can be used and later matured into whisky. The other two parts are returned to the process and therefore go into the next round of distillation. This ensures that as little of the valuable alcohol is lost as possible.
The challenge lies in determining what is foreshot, middle cut (new make) and what are feints. Where should the distiller place the cut?
Measuring devices in the spirit safe provide the distiller with two important values:

• The temperature of the distillate and
• The density of the distillate measured with a hydrometer.

The exact point to make the cut will vary from distillery to distillery depending on the desired flavor profile. Depending on where the cut is placed, the distiller can determine the combination of methanol, ester, aldehyde and fusel oil.



The invention
The 'spirit sake' was originally invented in 1819 by James Fox. It was an attempt to create a single mechanical device that allowed the distillate to be monitored and controlled without coming into contact with the environment or evaporating. Little did James Fox know at the time that the authorities would subsequently take an extraordinary interest in his invention and that it would become the government's weapon against illegal distilling.
With the passing of the "The Accise Act" in 1823, distilling was made legal if the distiller paid a fee of ten pounds and a duty for every gallon of pure alcohol produced. In order to put the new law into practice, the authorities had to keep a close eye on the now fully legal distillers. This was the beginning of the 'spirit safe' as a permanent installation in all distilleries.

The

authorities thus blocked free access to the freshly distilled drops by simply putting a padlock on the safe.

The keys to the safe!
Before 1983, there was actually only one key to open the padlock on the side of the safe. This key was kept by the customs department, whose job it is to control how much spirit is produced at a distillery. However, since 1983, the distillery manager has also had a copy of the key so that they could access the system if problems arose.
With the increasing digitization of the process, the spirit safe is unfortunately on its way out of Scottish distilleries. At best, some will survive and remain in distilleries for decoration and display to tourists. In many distilleries today, the process is controlled by computers and the distiller simply presses a button instead of reading gauges.